Blade locking device



4 R. N. ABILD 2,686,656 6 I BLADE LOCKING DEVICE Filed April 4, 1950 I 1713. 4. I g

Ill muf l6 Inventor R0 ari .III- 83:20? E0 or" Patented Aug. 17, 1954 UNITED STATES PATENT OFFICE BLADE LOCKING DEVICE Robert N. Abild, New Britain, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application April 4, 1950, Serial No. 153,985

6 Claims. 1 v

This invention relates to a device for locking blades in position in a supporting disc and is especially adapted for axial flow compressors or turbines. The rotor for a compressor or turbine is generally made up of one or more supporting discs each having a row of radially extending blades with the roots of the blades fitting in axially extending slots provided in the disc. The blade root is held in the slot by a blade lock which is preferably so constructed that removal of the blade from the disc will not necessitatedamaging of either the blade or the disc.

The copending Ledwith application Serial No. 153,795 filed April 4, 1950, having the sameassignee as this application, has a blade lock in the form of a strip extending from end to end of the slot that receives the blade root with tabs bent over at each end to engage the ends of the blade root and the sides of the disc. This arrangement is generally satisfactory except in certain cases especially where the blade root is relatively small and where the slot which receives the root is not perpendicular to the sides of the disc in which case the axial thrust on the blade tends to impart a twist to the locking strip within the base of the slot. A feature of this invention is an arrangement for preventing the twisting of the locking strip beneath the blade root. Another feature is an arrangement which eliminates the necessity for any tabs projecting over the ends of the blade root since especially in small size blades there is not always adequate room for the tab.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

Fig. 1 is a sectional view through a compressor disc showing the lock in position.

Fig. 2 is a perspective view of a portion of the disc with the blade and blade lock separated from the disc but in the proper axial relation.

Fig. 3 is a sectional view along the line 3-4! of Fig. 1.

Fig. 4 is a fragmentary sectional view of a part of Fig. 1 on a larger scale.

Fig. 5 is a bottom view of the blade root.

Fig. 6 is a plan view of the blade lock before insertion in the disc.

The invention is shown in a compressor disc although it will be understood that the invention is equallyapplicable for the locking of a turbine blade in a supporting disc. As shown, the disc 2 has a plurality of axially extending slots 4, Figs..2 and 3, which receive the correspondingly shaped blade roots 6 which support the radially extending row of blades 8. The blades are positioned in the disc by axial insertion and are held in position by the blade lock [0 hereinafter described in detail.

The blade root shown is the type commonly referred to as a dovetail in which the lower part of the blade root is brought to fit in a similarly shaped portion of the slot 4. Both the slot and the blade root narrow down to a relatively narrow neck portion I4 and both the slot and the blade root then widen so that the blade root has shoulders l6 which engage in similar grooves in the disc to support the blade against circumferential movement.

The blade lock 10 is in the form of a strip I6 which extends from end to end of the slot 4 and is sufficiently longer than the slot so that the ends may be bent downwardly to form tabs l8, Fig. 4, engaging with opposite side surfaces of the disc between the ends of the lock, the opposite side surfaces having notches 20 which receive proj ecting ribs 22, Fig. 5, on the underside of the blade root. These ribs are shorter than the length of the blade root as shown so that a portion of the blade look at each end of the blade root is supported for its entire width between the blade root and the base of the slot in the disc. In this way any tendency of the lock to twist as a result of the forces applied thereon by the axial thrust in the blade is counteracted by the broad end portions of the lock.

The preparation of the ribs 22 is not a complicated machining operation since these ribs may be produced by first machining a longitudinal slot 24, Fig. 5, which is the width of the narrow central portion of the blade lock and then by making transverse cuts 26 at opposite ends of the blade root thereby to reduce the length of the ribs 22 to correspond to the length of the notches 20. The blade root may be assembled in the disc by placing the blade lock in position between the ribs 22 with one of the tabs I8 bent downwardly as shown. After the blade has been inserted axially to the proper position the other tab I8 is bent down and the assembly is complete. Disassembly is readily possible either by bending up one of the tabs H3 or by completely breaking it, whichever is more convenient. It may be noted that this blade lock may be bowed somewhat between its ends, as in the case of the blade lock in the copending Ledwith application, above mentioned, for the purpose of maintaining the blade roots snugly in the slot in the disc.

It is to be understood that the invention is not 3 limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim: 7

1. In a rotor construction, a disc member having a series of axial slots extending through the disc at its outer periphery, a series of blades extending radially outward from the disc and each having a root member fitting in and engaging one of said slots, and locking means for each blade root to hold it in axial position in the slot,

said locking means comprising a flat sti'ip'of ma terial extending through said slot and located in the base thereof, said strip havingitsen'ds projecting beyond the ends of the slot and'havi'ng the projecting; ends extending over and engaging the sides of one of said members, said' strip having, a notch between its ends, said other member having a projecting rib thereon engaging with said notch to prevent relative axial movement therebetween; I Y 2'; In a rotor construction, a disc member having a series of axial slots extending through the discs'atits outer periphery, a series of blades each blade extending radially outward from the disc andhaving a-rootmember fitting in and engaging one'of said slots,'and locking means for each blade root tohold-it in axial position in the slot, said locking means comprising a flat strip of material'extending through "said slot and located" in the base thereof beneatlrthe blade root member, said' strip-having its 'endsprojectingb'eyond'the ends of the slo't'and having the projecting'ends extending overthe sides or" said disc,

said strip having at least one recess between its ends, and theblade'root member having a cooperating lug engaging with said" recess to prevent axial movement therebetween.

' 3. 'In a rotor construction, a disc having a series of axial slots extending'through the-disc at-the periphery and a'series'of blades extending radially outward'from the disc and eachbladehavinga root received in'one of said slots; said root being shaped to 'provide'a space between the bottom of said rootandthe base of the slot, in combination with a locking strip positioned in said space with the ends projecting beyond the ends of the slot,

said ends extending over 'andengaging the side surfaces ofthe" disc, said strip having; at least at one side; a notch betweenits ends, "said root having aprojectibn thereon to fit within the notch and thereby prevent relative movement be tween the'blade andfthe' locking strip.

4. In a rotcr'construction, a disc having a series of axially extending 'slots'in -the"periphery'andaserie's of blades" having rootsreceivedin said slots, each root being shapedto provide'a space between the bottorn'of said root'and the'base of the slotfin' combination with a locking strip positioned in said space with its ends extending over and engaging the side surfaces of the disc, said strip having its opposite side edges notched between the ends and said blade root having spaced projecting ribs thereon corresponding in dimension to the notches in the strip and engaging therewith to prevent relative axial movement between the blade and locking strip.

5. In a rotor 'confstructionia disd'h'a'ving a series of axially extending slots'in the periphery and a series of blades having roots received in said slots, each root being shaped to provide a space between the bottom of said root and the base of the slot, in combination with a locking strip positioned-in said space with its ends extending over and engagingt lieside surfaces of the disc, said strip having its opposite side edges notched between theends and-said blade root having spaced projecting ribs thereon corresponding in dimenrammes notches in the strip and engaging therewith to prevent relative axialmovement between the bladeand' lo' cking strip} the'ends of the strip outwardly of "the'notches being'subs'tanti'ally' the full width of the'slot'inthedisc and positioned between thebottom of the blade root and the base of the slot to be held thereby against twisting;

r 6.- In a rotorconstruction, a dis'cha ving' a series of axially extending-slots inthep'eriphery and a series'of blades having roots received in said slots, each root-being shapedto provide 'a spacebetween the bottom of said'root and the base of the slot, iii-combination with locking stripl-pjosfl tioned in said space wahas'ends extending over and engaging-the side surfaces of the disc; said strip having its opposite side edges notched be tween the ends and'said blade root having spaced projecting ribs thereon corresponding in dimen sion to thehotchesin the strip and engaging therewith to prevent relative axial movement be tween the blade and locking-strip; thespaced projectingribs on the blade rootfterminatingat V groove.

References Cited in the file of this patent N rEDf IA s ATENre 

